Would Knife Juggler trigger THREE times from Leeroy Jenkins entering play, since you are the one summoning the Whelps for the opponent, or would it only trigger once?

I know the wording leads us to believe that it would trigger three times, but what's the general consensus on this?

In this case, your Knife Juggler would only trigger once for Leeroy Jenkins and not with the two whelps that are spawned. The whelps are considered your opponent's and won't trigger effects for you. However, your opponent would get to throw two knives if he has a Knife Juggler in play and you play Leeroy Jenkins.